Opto-electronic modules are devices that combine optical with electrical devices in order to take advantage of capabilities presented by each field of technology. For instance, the optical devices open the door to optical transmission of signals, which allows for very high data transmission bandwidths. On the other hand, the electrical devices provide the ability to perform the conventional operations of storing and manipulating the transmitted signals. Generally, an optical device is directly or indirectly attached to a semiconductor device such that the optical device sends and receives optical data signals and the semiconductor device converts the optical signals to electrical signals. These converted electrical signals can then be manipulated with standard semiconductor devices, for example, a chip set. The opto-electronic module usually includes the combined optical and electrical devices which are inserted within a protective case. This case allows the module to be easily and safely handled during the construction of a system for computing, transmissions, or the like.
These opto-electronic modules are produced by numerous equipment manufacturers. As such, dimensional standards for opto-electronic modules have developed so that modules produced by various manufactures can fit with various systems. These standards are also referred to as “form factors.” Typically, an OEM will require a standard form factor which in turn forces component suppliers to work together and develop a set of fixed constraints (e.g. footprint dimensions, electrical pinout, connector type). One such standards agreement is the Multi-Source Agreement for Small Form Factor Pluggable (SFP) Modules (for Gigabit Ethernet and FiberChannel applications). These form factors are typically application specific. In most cases, the standards are confined to outer dimensions of a module, which define how a module should mechanically interface with other systems. For example, the positioning of it's electrical and/or optical ports are usually required to be within specific positions with respect to each other. One such requirement is the height of each of the optical and electrical ports from a bottom surface of an opto-electronic module. In another case, the relative difference in height of the optical and electrical ports is specified to be within a certain dimensional window.
The dimensional requirements internal to the module, i.e., within the protective case, are not usually specified because the internal architecture is left to the suppliers' discretion for design, component selection, and integration. The chosen internal architecture must only ‘fit’ within the standard form factor package and interface to electrical and optical Inputs/Outputs.
Currently, opto-electronic modules are designed such that conventional optical and electrical components fit within standard form factors. For instance, many configurations for optical and electrical components are suited for use of TO can optical components. Many optical components are connected to the electrical components through wires that transmit conventional singled ended electrical signals. Single ended signals are commonly used in interfaces and buses within computing systems due to its simplicity and ease of implementation. Single ended signals are transmitted by using a positive voltage as a “one” and a zero voltage (ground) as a “zero.” Unfortunately, problems within a bus or an port can arise due to bouncing signals, interference, degradation over distance and cross-talk from adjacent signals. These problems become more severe as the speed of a system increases, the longer a transmission distance becomes (e.g., when the length of a cable increases). As a result, the length of the wires that connect the optical devices and the electrical devices are very limited. The short wires provide little room for adjusting the position of the optical device with respect to the electrical device such that the optical and electrical ports are positioned within a required positional window. This is increasingly problematic as the transmission speeds of opto-electronic modules increase since the length of the wires further shorten. The limitations created by the wire length thereby cause opto-electronic systems to be quite inflexible to accommodating optical and electrical devices of various types and shapes (e.g., alternative lower cost, higher reliability, and higher data rate components). Such inflexibility also limits the types of materials that can be used within an opto-electronic module.
FIGS. 1–3 illustrate diagrammatic views of a common opto-electronic (OE) module 100 according to the current state of the art. OE module 100 can be used, for example, for serving as the intermediate connector between optical fibers and a computer, mainframe, router, switch, or the like. It could be said that opto-electronic module 100 is similar to a small form factor pluggable (SFP) manufactured by Agilent Technologies, model number HFBR-5720L. Information about model number HFBR-5720L can be found at www.Agilent.com. FIG. 1 illustrates a perspective view of OE module 100. OE module 100 includes a case 102 having openings 104 and 106 at each end in order to provide access to the internal components contained within case 102. Opening 104, referred to as an optical interface opening 104, provides access to the optical devices 108, which are used to send, receive, or send and receive optical signals from optical transmission mediums such as optical fibers. The mechanical components for making a connection between optical devices 108 and optical transmission mediums are collectively referred to as an optical port. In FIG. 1, optical port 110 includes the cylindrical tubes that present themselves at optical interface opening 104. Each cylindrical tube of optical port 110 is shaped to receive an optical transmission fiber. Opening 106, referred to as an electrical interface opening 106, provides access so that an electrical connection between electrical contacts of the internal components can be made with an electrical system that is external to the OE module 100. The internal components will be more clearly shown in the following FIGS. 2 and 3.
Case 102 should have a shape that allows OE module 100 to fit into and within systems that intend to incorporate module 100. As discussed earlier, many manufacturers produce OE modules in compliance with standards agreements in order to ensure interoperability with various systems. For instance, the outer dimensions of case 102, the size, height and other specifics regarding openings 104 and 106, and the position and size of the optical and electrical ports, are just some of the proportions of OE module 100 that might be required to within certain dimensional constraints. Other specifics such as material composition may also be required to satisfy certain criteria.
FIG. 2 illustrates a cross-sectional view of OE module 100 along line 2—2. FIG. 2 shows the internal components of OE module 100 positioned within case 102. FIG. 3 will also be referenced along with FIG. 2 since FIG. 3 illustrates a perspective view of the internal components of OE module 100. The internal components include the optical devices 108 and a single printed circuit board (PCB) 112, which supports various semiconductor chip packages 114 and electrical components 116 (e.g., transistors, capacitors, and the like). Optical port 110 is shown as protruding out of optical interface opening 104 for connection with optical transmission mediums. An electrical port 118 formed at one end of the PCB 112 is designed for connection with an external system (e.g., a router or a switch). Electrical port 118 includes electrical contacts 120 formed on the top and/or bottom surface of PCB 112. Printed circuitry lines 122 run across the surface of PCB 112 to connect electrical contacts 120 and other components on PCB 112 with each other.
As shown in FIG. 3, but more clearly in FIG. 2, optical devices 108 are connected to PCB 112 through electrical wires 124. Since optical devices 108 are designed to output singled ended signals, wires 124 must be an appropriate length so that electrical properties are maintained at a certain level. For instance, the length of wires 124 should be short enough so that electrical parasitics (specifically, inductance) levels can be minimized. With today's high transmission requirements, the length of wires 124 are desirably kept to a minimum. Unfortunately, this limits the range in which optical device 108 can be positioned relative to PCB 112. More importantly, this affects the range in which the optical port 110 can be positioned with respect to the electrical port 118. Standards agreements typically will require that the optical plane height 126 be within a certain height range with respect to the bottom 128 of OE module 100. The optical plane is typically, the height at which the optical device 108 connects with an optical fiber. Such requirements also require that the electrical plane height 130 be within a certain height range with respect to the bottom 128 of the OE module 100. Some requirements pertain to having the optical plane height and the electrical plane height within a certain distance from each other. Ultimately, the short wires 124 limit the flexibility of positioning the optical port 110 with respect to the electrical port 118. This is especially problematic when changes to the components within OE module 100 are desired.
Other common OE modules include model number FTRJ-1321-7D by Finisar and model number V23818-M305-B57 by Infineon Technologies AG.
In view of the foregoing, an opto-electronic module that is flexible in design such that opto-electronic modules of different types and dimensions can be properly contained within a case that complies within dimensional standards requirements would be desirable.